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Moggill, Australia

Charlton B.D.,University of Vienna | Ellis W.A.H.,Central Queensland University | Larkin R.,Moggill Koala Hospital | Tecumseh Fitch W.,University of Vienna
Animal Cognition | Year: 2012

Advances in bioacoustics allow us to study the perceptual and functional relevance of individual acoustic parameters. Here, we use re-synthesised male koala bellows and a habituation-dishabituation paradigm to test the hypothesis that male koalas are sensitive to shifts in formant frequencies corresponding to the natural variation in body size between a large and small adult male. We found that males habituated to bellows, in which the formants had been shifted to simulate a large or small male displayed a significant increase in behavioural response (dishabituation) when they were presented with bellows simulating the alternate size variant. The rehabituation control, in which the behavioural response levels returned to that of the last playbacks of the habituation phase, indicates that this was not a chance increase in response levels. Our results provide clear evidence that male koalas perceive and attend to size-related formant information in their own species-specific vocalisations and suggest that formant perception is a widespread ability shared by marsupials and placental mammals, and perhaps by vertebrates more widely. © 2012 Springer-Verlag.

Charlton B.D.,University of Vienna | Ellis W.A.H.,University of Queensland | McKinnon A.J.,Moggill Koala Hospital | Cowin G.J.,University of Queensland | And 3 more authors.
Journal of Experimental Biology | Year: 2011

Determining the information content of vocal signals and understanding morphological modifications of vocal anatomy are key steps towards revealing the selection pressures acting on a given species' vocal communication system. Here, we used a combination of acoustic and anatomical data to investigate whether male koala bellows provide reliable information on the caller's body size, and to confirm whether male koalas have a permanently descended larynx. Our results indicate that the spectral prominences of male koala bellows are formants (vocal tract resonances), and show that larger males have lower formant spacing. In contrast, no relationship between body size and the fundamental frequency was found. Anatomical investigations revealed that male koalas have a permanently descended larynx: the first example of this in a marsupial. Furthermore, we found a deeply anchored sternothyroid muscle that could allow male koalas to retract their larynx into the thorax. While this would explain the low formant spacing of the exhalation and initial inhalation phases of male bellows, further research will be required to reveal the anatomical basis for the formant spacing of the later inhalation phases, which is predictive of vocal tract lengths of around 50cm (nearly the length of an adult koala's body). Taken together, these findings show that the formant spacing of male koala bellows has the potential to provide receivers with reliable information on the caller's body size, and reveal that vocal adaptations allowing callers to exaggerate (or maximise) the acoustic impression of their size have evolved independently in marsupials and placental mammals. © 2011. Published by The Company of Biologists Ltd.

Charlton B.D.,University of Vienna | Ellis W.A.H.,University of Queensland | McKinnon A.J.,Moggill Koala Hospital | Brumm J.,Lone Pine Koala Sanctuary | And 2 more authors.
PLoS ONE | Year: 2011

The ability to signal individual identity using vocal signals and distinguish between conspecifics based on vocal cues is important in several mammal species. Furthermore, it can be important for receivers to differentiate between callers in reproductive contexts. In this study, we used acoustic analyses to determine whether male koala bellows are individually distinctive and to investigate the relative importance of different acoustic features for coding individuality. We then used a habituation-discrimination paradigm to investigate whether koalas discriminate between the bellow vocalisations of different male callers. Our results show that male koala bellows are highly individualized, and indicate that cues related to vocal tract filtering contribute the most to vocal identity. In addition, we found that male and female koalas habituated to the bellows of a specific male showed a significant dishabituation when they were presented with bellows from a novel male. The significant reduction in behavioural response to a final rehabituation playback shows this was not a chance rebound in response levels. Our findings indicate that male koala bellows are highly individually distinctive and that the identity of male callers is functionally relevant to male and female koalas during the breeding season. We go on to discuss the biological relevance of signalling identity in this species' sexual communication and the potential practical implications of our findings for acoustic monitoring of male population levels. © 2011 Charlton et al.

Charlton B.D.,University of Sussex | Frey R.,Leibniz Institute for Zoo and Wildlife Research | McKinnon A.J.,Moggill Koala Hospital | Fritsch G.,Leibniz Institute for Zoo and Wildlife Research | And 2 more authors.
Current Biology | Year: 2013

During the breeding season, male koalas produce 'bellow' vocalisations that are characterised by a continuous series of inhalation and exhalation sections, and an extremely low fundamental frequency (the main acoustic correlate of perceived pitch) [1]. Remarkably, the fundamental frequency (F0) of bellow inhalation sections averages 27.1 Hz (range: 9.8-61.5 Hz [1]), which is 20 times lower than would be expected for an animal weighing 8 kg [2] and more typical of an animal the size of an elephant (Supplemental figure S1A). Here, we demonstrate that koalas use a novel vocal organ to produce their unusually low-pitched mating calls. © 2013 Elsevier Ltd.

Melville D.F.,University of Queensland | O'Brien G.M.,University of New England of Australia | Crichton E.G.,University of Queensland | Theilemann P.,Moggill Koala Hospital | And 2 more authors.
Theriogenology | Year: 2012

Effective contraception would enhance genetic management of captive Pteropus species, which typically breed well in captivity. Male reproductive seasonality was monitored (15-mo interval) in captive P. alecto (6 controls and 5 treated with 4.7 mg deslorelin). In untreated males, there were seasonal changes in testicular volume, body weight and testosterone secretion; testicular volume and body weight peaked in February and March, respectively, whereas testosterone concentration remained >5 ng/ml before rising (P < 0.001) to 24.9 ± 3.6 ng/ml (mean ± SEM) in April. However, there was no corresponding change in sperm quality, and seminal vesicle gland (SVG) secretions remained present in ejaculates. In treated males, testosterone concentration had an initial 'flare' response (mean ± SEM peak: 19.95 ± 3.27 ng/ml) before declining (P < 0.001) by 32 d to basal levels, where it remained. In these males, there was reduced sperm motility after 1 mo (P < 0.001) and the absence of SVG secretions after 4 mo. However, aspermic ejaculates were first recorded 5 mo post-treatment. At 10 mo after treatment, spermatogenesis was still disrupted, when membrane-intact, but non-motile sperm were present in two individuals. Motile sperm were first recovered from one of these males 13 mo after deslorelin treatment. We concluded that captive P. alecto males: (a) had seasonal reproductive changes in testicular volume, body weight and testosterone secretion; (b) produced motile, membrane-intact sperm and SVG secretions throughout the year; and (c) had a rapid decline in testosterone concentration and consequent suppression of testicular function for at least 5 mo following deslorelin administration. © 2012 Elsevier Inc.

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